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More efficient methods are needed for the in-situ evaluation of mass transfer parameters which describe the movement of solutes through aquifer material. The objective of this study was to develop a method for estimating diffusion rate and capacity coefficients using a single-well, "push-pull" tracer test. The method consists of the pulse-type injection of a test solution into the saturated zone of an aquifer through the screen of an existing monitoring well. This is followed by a resting (diffusion) period, after which the test solution is extracted from the same well. During the extraction phase a concentration breakthrough curve is obtained. The method uses numerical simulations of the extraction phase breakthrough curve to estimate mass transfer parameters. The methodology was evaluated using a series of laboratory-scale experiments which were performed in a Physical Aquifer Model (PAM). The sediment pack contained in the PAM was modified to create an immobile region governed by diffusive processes. Results from four laboratory-scale experiments are inconclusive in determining the ability of the method to determine mass transfer parameters. Experimental difficulties contributed a significant source of error during the method evaluation. The resting period between the injection and extraction phase was to allow diffusion into the initially solute-free immobile region. Evidence suggests solute was introduced into the immobile region by advective processes during the injection phase of the experiments. Additional experimental work is required to evaluate the methodology. This may include either laboratory or field-scale evaluation of the test method. / Graduation date: 1999

Responses of biological indicators of soil quality to winter cover cropping were measured on soil samples collected from 6 commercial growers' fields and two experiment research stations in the Willamette Valley of Oregon. The research stations were the North Willamette Research and Extension Center (Aurora, OR), and the Oregon State University Vegetable Farm (Corvallis, OR). The research stations and five on-farm sites compared winter cover crops or winter fallow in rotation with a summer vegetable crop. In one on-farm site, minimum tillage or conventional till following winter cover crops was compared. The objectives of this study were to: 1) monitor changes in soil biological properties under field managed with cover crops; 2) test potential of buried cotton strip as indicator of soil biological activity and as a soil quality index; and 3) assess the degree of correlation between tensile strength and cotton strip weight loss. The major findings were: 1) microbial biomass carbon and ��-glucosidase activity were the most sensitive to cover crop management; 2) cotton strip decomposition was correlated to soil biological properties but was not very sensitive to management changes; and 3) that measuring weight loss was nearly as effective as tensile strength in assessing cotton strip decomposition in soils. / Graduation date: 1999

In addition, the vanishing viscousity limit of the solutions for viscous lake equations with the Navier type boundary conditions is obtained for both the smooth and non-smooth initial data. / The aim of the thesis is to understand the dynamics and interactions between the Ekman layer and thermal layer which are very important issues in the studies of geophysical flows. We obtain some new results on the primitive equations of the atmosphere and the incompressible Navier-Stokes equations with rotating terms. We study the asymptotic limits of the solutions to the initial boundary value problem for the three dimensional primitive equations. We have constructed the asymptotic ansatz which is uniformly valid up to the boundary to derive the quasi-geostrophic equations and the corresponding boundary layer systems. These equations are also important and widely studied in the geophysical flows. The uniform convergence to the solutions for quasi-geostrophic equations is obtained rigorously. / Niu Dongjuan. / "June 2006." / Adviser: Zhouping Xin. / Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1675. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 96-106). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Graduation date: 1994

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OWRT Project No. B-052-ARIZ / Agreement No. 14-34-0001-7136 / Project Dates: October 1976 - December 1977 / Includes authors' paper, "Foundational theories of solute transport in porous media: a critical review."

This research presents a new, more efficient computational scheme for complex periodic flows, and brings forward two novel ideas. The first consists in the use of a Fourier space time representation in conjunction with a high-order spatial discretization. The second is based on the efficient treatment of the resulting set of equations using a fast, implicit solver. This thesis describes the formulation and implementation of the proposed framework. Firstly, a high-order spectral difference scheme for the Euler equations is introduced. Secondly, the non-linear frequency domain method resolving the unsteady behavior of the flow is discussed. Thirdly, a mathematical and experimental validation of the proposed algorithm is carried out. Numerical experiments performed in this thesis suggest that the methodology could be an attractive new avenue for large scale time-dependent problems, alleviating the computational cost traditionally associated with such simulations.